After most of the snow inside the Rim has melted away, there remains an almost continuous accumulation below The Watchman and Hillman Peak. These snowbanks are separated from the lake by a very definite border of rather large rock fragments. When finally the warmth of summer has completely or partially melted these snowbanks, there exist depressions where the snow was formerly present. In the latter season of the year, the trough is conspicuous but might not be accorded its true origin.

The manner in which the ridge and trough are formed is revealed by the processes which are especially active while the snowbanks are present. Occasionally a rock fragment, from the cliffs or slopes above, tumbles toward the lake an in doing so is carried across the snow. This process has been repeated until the accumulation finally became so great that it was built above the water and the ridge character was developed. The predominance of large size fragments in the ridge is noteworthy and is due to the high velocity attained by the falling rocks. As a result of this inertia, the large fragments are propelled across the snow whereas the smaller fragments are stopped by the snow.

Thus the sorting and accumulation of such loose material into these shore ridges is principally a geological feature whose origin is associated with the season of snow at Crater Lake.